Something we see here in AZ many times a year. Folks come here and just do not understand the effect of the heat and dry air. You can sweat out in an hour or two. Note the temps this week have been hitting 115 in Phoenix and up to 118 elsewhere in AZ. Something which surprises folks at the Grand Canyon is that the South Rim where all the resort stuff is at over 7000 ft. It is nice there even on very hot days. But at the river level the elevation is near the same as Phoenix so if it is 115 in Phoenix it is likely above 110 in the lower parts of the canyon. And the heat really radiates off the rocks.

http://www.therepublic.com/view/stor...on-Hiker-Death